1.Technical Field
The present invention relates to techniques of protecting programs against unauthorized alteration and analysis.
2.Background Art
In recent years, the widespread use of PCs and the Internet makes it possible to copy or edit digital content such as software easily. This being so, tamper-resistant techniques are needed to protect software against unauthorized alteration and analysis.
Research has long been performed on tamper-resistant techniques. For example, an article “Protecting Software against Inverse Analysis and Falsification” in Nikkei Electronics, Jan. 5, 1998, pp. 209-220 describes basic principles and concrete methods for preventing unauthorized software analysis. Also, an article “Software Tamper-resistant Techniques” in Fuji Xerox Technical Report, No. 13, pp. 20-28 deals with technical problems and measures concerning prevention of unauthorized software analysis.
Despite this research, more various techniques for protecting programs against malicious users are still needed.